One of the essential events that facilitate the effective multiplication of Plasmodium in the peripheral represents the rapid reinvasion of erythrocytes by released merozoites. Despite extensive morphological studies the biochemical mechanisms of the merozoite-erythrocyte interaction and the nature of the newly-formed parasitopherous membrane are largely unknown. Most recent advances in single cell spectroscopy, available in our laboratory, combined with high resolution, chromatographic lipid analyses should allow us to examine the following problems: (1) large scale isolation and purification of infective merozoites; (2) study of the merozoite-acceptor membrane interaction using (a) erythrocytes, (b) sealed, pink erythrocyte ghosts, and (c) large unilamelar liposomes with incorporated glycophorin A and/or human erythrocyte band 3 protein. Arrest of the merozoite invasion at various phases. (3) Study of the merozoite-target interaction at the single cell level by (a) video-intensified fluorescence microscopy (VIFM); (b) laser Raman microprobe spectroscopy, both linked to (c) computerized image analysis. (4) Use of fluorescent probes and VIFM to evaluate (a) state and distribution of membrane lipids and (b) transmembrane potential, intracellular pH and [Ca2+]. (5) Use of Raman microprobe to examine lipids using (a) deuterated lipid probes and (b) carotenoid probes. (6) Employment of radiolabeled target membrane phospholipids/cholesterol to measure (a) possible phospholipase activation and/or (b) cholesterol exchange.